When the Society for Neuroscience gets together for their annual meeting each year, a city of scientists suddenly forms for a week. This year’s meeting has drawn 31,000 people to the Washington DC Convention Center. The subjects of their presentations ranged from brain scans of memories to the molecular details of disorders such as Parkinson’s and autism. This morning, a scientist named Svante Paabo delivered a talk. Its subject might make you think that he had stumbled into the wrong conference altogether. He delivered a lecture about Neanderthals.
Yet Paabo did not speak to an empty room. He stood before thousands of researchers in the main hall of the convention center. His face was projected onto a dozen giant screens, as if he were opening for the Rolling Stones. When Paabo was done, the audience released a surging crest of applause. One neuroscientist I know, who was sitting somewhere in that huge room, sent me a one-word email as Paabo finished: “Amazing.”
You may well know about Paabo’s work. In August, Elizabeth Kolbert published a long profile in the New Yorker. But he’s been in the news for fifteen years. I’ve also followed his work since the mid-1990s, having written about pieces of Paabo’s work in newspapers, magazines, and books. But it was bracing to hear him bring together the scope of his research in an hour-including new experiments that Paabo’s colleagues are presenting at the meeting. He has changed the way scientists study human evolution. Along with fossils, they can now study genomes that belonged to people who died 40,000 years ago. They can do experiments to see how some of those individual genes helped to make us human. During his talk, Paabo used this new research to sketch out a sweeping vision of how our ancestors evolved uniquely human brains as they swept out across the world.
Before the 1990s, scientists could only study the shape of fossils to learn about how we evolved. A million years ago, the fossil record contained evidence of human-like creatures in Europe, Asia, and Africa. Roughly speaking, the leading hypotheses for how those creatures became Homo sapiens came in two flavors. Some scientists argued that all the Old World hominins were a single species, with genes flowing from one population to another, and together they evolved into our species. Others argued that most hominin populations became extinct. A single population in Africa evolved into our species, and then later spread out across the Old World, replacing other species like Neanderthals in Europe.